Mortality from breast cancer is stage-dependent and thus, early detection is vital if we are to make progress addressing the burden of this disease. Imaging methods such as mammography have made a ma contribution in the early diagnosis of breast cancer. Yet is clear that the standard imaging techniques have significant limitations in detecting the earliest changes of breast cancer and in distinguishing benign condition from important premalignant and malignant disease. Based on the remarkable efficacy of simple palpation as a clinical tool for detecting cancer in accessible parts of the body, it has long been recognized that a sensitive, imaging-based method, capable of assessing viscoelastjc properties of tissue, might offer considerable potential for discriminating malignant from benign tissues. The goal of this research is to develop a practical noninvasive MRJ-based method for quantitatively evaluating the mechanical properties of breast tissues. We call this technique magnetic resonance elastography (MRE). Preliminary development of MRE in our laboratory has demonstrated the feasibility of quantitatively imaging the large differences in the elastic properties of normal and cancerous breast tissues in vivo. The specific aims of this proposal are (1) to further develop the MR elastography technology for pre imaging and (2) to assess the potential of this new imaging technique to differentiate breast malignancies fr non-malignant lesions. The MRE technique is implemented on a standard MRI scanner. Therefore it is readily combined in the same examination with standard contrast-enhanced MRI protocols for breast cancer imaging. This research-will provide the first substantial body of quantitative, spatially-resolved data describing the viscoelastic properties of benign and malignant breast tissues in vivo. The planned technical development work and pilot studies will provide critical prerequisites for determining the advisability and most efficient design of a future clinical trial to test the value of MRE for distinguishing benign from malignant breast masses.